The finches of the Galapagos Islands were crucial in the development of Charles Darwin's theory of evolution, and now scientists have figured out what genetic changes gave them their ever-evolving beaks. Their research, published Wednesday in the journal Nature to coincide with Thursday's 206th anniversary of Charles Darwin's birth, reveals the genetic "smoking gun" of the finches' rapid evolution.

After his voyage around the Galapagos Islands in 1835, Darwin realized that the finches living there were related — but markedly different when it came to their beak shapes.